The start of 2018 has been off a wild start. After a colder and snowier than average winter season and a spring that can't seem to make up its mind, many in Central Illinois are wondering what kind of weather might we see this upcoming summer.
After late-season record cold and record snows, April 2018 proved to be one of the coolest Aprils on record for the contiguous United States and the 2nd coolest on record for the state of Illinois. Now, halfway through the month of May, summer appears to have arrived early. Temperatures have been consistently above average since the start of the month across much of the U.S. making it one of the warmest Mays on record.
The Impact of the El Nino Southern Oscillation
In late 2017 and early 2018, La Niña conditions were seen across the Pacific Ocean which, in part, led to some of the colder and snowier conditions we saw this past Winter and early Spring. Now, La Niña conditions have faded and neutral conditions are in place. The current forecast calls for neutral conditions to persist through the summer and into early fall before we potentially see weak El Niño conditions take shape by next winter.
An average summer in Peoria would yield an average daily temperature of 73.8° and 10.80" of rainfall. Looking back at past summers where La Niña conditions were fading in the Spring, Central Illinois would go on to see a cooler than normal and drier than normal Summer. The U.S. experienced similar conditions back in 1962 where a long winter season was followed up by a rather warm May. Following the wild swings in temperature between April and May, cooler than normal conditions returned through the summer and the region saw below average precipitation.
With very similar conditions in the past, it seems plausible that we could see those conditions take shape again this summer, with perhaps a few minor differences.
The Climate Prediction Center's Outlook
The Climate Prediction Centers early summer outlook calls for above-average temperatures across much of the U.S. with an equal chance of seeing above, below or near average temperatures across the Central Plains and Midwest. They are also calling for above-average precipitation across the Northeast while leaving the Central Plains and the Midwest with an equal chance of seeing above, below or near average precipitation.
My Bold Prediction
I'm leaning much of my forecast on the events from the past. While El Niño conditions may develop by the end of the year, the impacts from that potential El Niño likely won't be realized until this winter. Climate models have also hinted at periods of cooler and even wetter than normal conditions through June, July, and August, though they have remained inconsistent as to exactly when those periods will come.
I think that Central Illinois will see near to below average temperatures over the summer months with the typical late summer heat and humidity returning in August. This means it looks like June and July could be cooler than average.
As for precipitation, I've taken a bit of an optimistic stance. While it has been dry recently, the pattern has provided us many chances to receive some moisture. I think that pattern will carry over into summer and may even be boosted a little bit if the jet stream becomes a little more amplified in June and July. I think that Central Illinois will make up some ground when it comes to rainfall and we'll receive somewhere between 9 and 12 inches of rain from June through August. This would mean the area would see near to above average precipitation.
Severe Weather Outlook
The 2018 severe weather season has been off to a very slow start. Thanks to colder than normal conditions in April and sudden change to summer-like conditions in May, there haven't been many opportunities for severe weather. Things could quickly change in June if the Jet Stream does indeed drift a little further south.
On average, June is the 3rd most active month when it comes to tornadoes touching down in Illinois. So while the season has been off to a quiet start, it only takes one big event to make it a really bad season.